1. Field of the Invention
The present invention is related to computer systems, and specifically to computer systems executing software having different criticality in mission-critical applications.
2. Description of the Prior Art
Different kinds of computer systems and software are being used to an increasing extent within many different fields for performing more and more tasks. This use has also increased within fields with very high reliability requirements, such as nuclear power and avionics. The software that are required to always be operational for these possibly life and death applications to perform their tasks are generally categorized as mission-critical. As the performance of computer systems increases, so has the amount of software installed in and executed by the same computer system. Additionally, the complexity of the software has also increased. However, not all software in a computer system is equally mission-critical. In such situations, the “mission-criticality” in this description and the following claims is related to how mission-critical certain software is to the overall functioning of a system. That is, how serious are the consequences when the software does not work. Software of high mission-criticality is very important and essentially always has to work, whereas the function of software with lower mission-criticality is not as important or essential to the operation of the system. Developing software that maintains high mission-criticality is, however, very costly compared to development of software of lower mission-criticality. When there is software of different mission-criticality in a computer system, there is a risk of software of lower mission-criticality affecting software of higher mission-criticality. This implies that software of lower mission-criticality, which in a computer system is intended to cooperate with software of higher mission-criticality, also has to be developed to comply with the requirements for the higher mission-criticality, which results in large development costs for the software.